This invention relates to an open-end spinning machine with facilities for the simultaneous piecing of thread at all spinning units and with centrally controlled drive mechanisms for the sliver feeding devices, for the sliver opening devices, for the spinning rotors, for the devices to take off the spun threads and to wind same onto bobbins, and for devices to produce a vacuum in housings surrounding the spinning rotors.
It has been contemplated to provide a so-called stop-start program to realize a combined piecing of all spinning units in open-end spinning machines. In this process, the shutting off of the spinning machine is conducted in a specific manner so that the thread, which breaks when the open-end spinning machine is turned off, does not leave the zone of the thread take-off duct so that the thread can be returned into the spinning rotor. Besides, a thread reserve is formed which is opened up during the startup of the open-end spinning machine so that the thread is sucked back into the spinning rotor. In this method, the final thread end produced upon the arrest of the machine has an overtwisted taper. During the startup of the machine, this taper of the threads results in poor piecing locations, the so-called corkscrews. This flaw in the yarn is in most cases made even worse because the thread end is once more overtwisted during the piecing operation. Under practical conditions, the observations is made in open-end spinning machines operating according to such methods that the piecing step is unsuccessful in a relatively high percentage of the spinning units so that an operator must piece the thread manually subsequently at such locations. This causes considerable difficulties in case the open-end spinning machine runs at relatively high rotor speeds, since then the piecing operation in principle is substantially more difficult.
Moveable piecing devices have likewise become known which are moved along an open-end spinning machine, executing an automatic piecing operation at the individual spinning stations. Such mobile piecing devices are intended particularly for eliminating the thread breaks occurring during operation at individual spinning stations. In a conventional type of construction (DOS [German Unexamined Laid-Open Application] No. 2,350,840) a cleaning step precedes the piecing operation proper, by which all essential parts of the respective spinning unit are subjected to a cleaning action. The reason for this is that it has been found that the occurrence of contaminations of the spinning unit and especially dirt in the spinning rotor is a cause for most of the thread break and also for flaws in the yarn. For this reason, the conventional type of structure provides furthermore to arbitrarily cause a thread break after a certain operating period and then to execute a cleaning and piecing operation. This makes it possible to ensure an extensively uniform yarn quality. It is possible to utilize such a mobile piecing device in order to start up an open-end spinning machine after it has come to a standstill. However, it should be kept in mind that in such a case a relatively large amount of time is consumed until all of the spinning units of the open-end spinning machine have commenced operation. This piecing time becomes shorter if several mobile piecing devices are present. However, this results in increased expenditure, inasmuch as the piecing devices are not cheap.
The invention is based on the problem of fashioning an open-end spinning machine of the type described hereinabove so that a combined piecing of all spinning units can be executed, wherein a maximally high quota of success is provided without having to incur excessive expenditures from a manufacturing viewpoint for each spinning unit.
This problem is solved by providing a program control for the drive mechanisms at least for the startup operation, thus controlling the instants at which the drive mechanisms are placed in operation; and by arranging, for the preparation of all spinning units for the combined piecing step, at least one servicing device movable to the individual spinning units which is equipped with means for seizing the threads and for returning same to the spinning rotors.
By means of this construction, a combined piecing operation becomes possible without having to design the individual spinning units in a special way or having to include therein additional operating elements which would increase the manufacturing expenditure. Yet, a rapid and safe piecing operation is thus obtained, since the mobile servicing device can readily be constructed so that it operates very exactly. Since the elements used in this mobile servicing device need to be present only once (no duplicates being required), a relatively high expenditure for same is worthwhile. The servicing device can execute the preparation work after the open-end spinning machine has been arrested or before it is placed in operation, so that the time necessary for the preparation of the spinning units is not lost in the form of operating time.
In a further development of the invention, the provision is made to equip the servicing device or devices with means for cutting the threads to a certain length and for preparing the thread ends. It is thereby made possible to further enhance the successful operation of the combined piecing method and to produce thread piecing places of high quality. The less satisfactory end of the thread produced before the open-end spinning machine was turned off is not utilized for the piecing operation, since this could impair the success.
In a further embodiment of the invention, the servicing device or devices have means for feeding the thread ends to thread take-off ducts of the spinning units. A return of the thread end into the spinning rotors is then readily possible if, during the operation of the servicing device, the vacuum generation of the open-end spinning machine has been maintained. However, if the open-end spinning machine is to be turned off entirely, then another embodiment of this invention provides that the servicing device includes a suction nozzle which can be selectively associated with connections of the housings of the spinning units surrounding the spinning rotors. In this case, the servicing device proper generates the vacuum, which latter is utilized for sucking the thread ends into the spinning rotors. For the same purpose, another embodiment of the invention provides that the servicing device or devices are equipped with an injection nozzle which can be associated with the thread take-off ducts including the threads. In this connection, the thread end is blown into the zone of the spinning rotors, so that here again the open-end spinning machine can remain in the turned-off condition entirely.
In a further development of the invention, the servicing device or devices include means for cleaning the spinning units. In this connection, the starting point is the consideration that it is expedient, in order to obtain a favorable thread quality, to create the same conditions at all spinning stations before the open-end spinning machine is placed in operation, by cleaning all of the spinning units. Thereby, a uniform thread quality can be attained.
In a further embodiment of the invention, the means of the servicing device or devices are combined into several, independently operable functional groups. This makes it possible to render the total mode of operation more economical, inasmuch as the individual functional groups can operate simultaneously at various spinning units. In this connection, it is advantageous to divide the servicing device or devices into a functional group executing the cleaning of the spinning units and a functional group accomplishing the seizing, cutting to length, preparation, and return of the thread ends to the spinning rotors.
In a further development of the invention, the functional group executing the seizing, cutting, preparing, and introduction of the thread ends into the spinning rotors is part of a mobile piecing device provided with additionally activatable means for taking off the thread returned to a spinning rotor and preferably with means for taking over and/or controlling the drive mechanisms for the installations for the feeding of the sliver and for the take-off and windup of the spun thread. This makes it possible to further exploit the mobile servicing device in that it is used, during normal operation, as a mobile piecing apparatus which effects a monitoring of the operation.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.